1. Field of the Invention
The invention relates in general to sheaves suitable for driving members via the traction developed between stranded wire ropes, which contact the sheave, and more specifically to such sheaves having treaded elastomeric grooves.
2. Description of the Prior Art
The rating of the drive machine connected to drive the sheave of a traction elevator system is determined by the traction efficiency. The traction efficiency may be improved by increasing the tractive effort for a given rope tension, or by maintaining a predetermined tractive effort while reducing the rope tension required to produce it.
While increasing the tractive effort for a given rope tension is desirable, it is only desirable up to a predetermined point, as it is essential that rope slippage occurs when the counterweight reaches an end of its travel path. Treaded elastomeric grooves have been used in the prior art to increase traction efficiency, with the relationship of the surface area of the treads versus the area of the spaces between the treads, being used to select the tractive effort. The tractive effort, however, increases with tread wear, and it is important to replace the elastomeric insert before the wear becomes significant. It would thus be desirable to reduce the wear rate of the treads, in order to extend the useful operating life of the elastomeric treads.